1. Field of the Invention
The present invention relates to an exposure apparatus for exposing a substrate to an energy in a vacuum.
2. Description of the Related Art
An extreme ultraviolet radiation (EUV) exposure apparatus and an electron beam exposure (drawing) apparatus which are currently developed as a next generation semiconductor exposure apparatus exposes a substrate to an energy in a vacuum environment. Since heat is not transferred by convection in a vacuum environment, heat is liable to accumulate within an object. For this reason, in the above exposure apparatus, countermeasures against heat are one of important developmental elements.
As one of the countermeasures against heat, there is a method for circulating a cooling fluid through the structure of the exposure apparatus. This method, however, vibrates the structure along with the circulation of the fluid, so that the method must be carefully applied to the exposure apparatus of which high resolving power and overlay accuracy are required. Japanese Patent Application Laid-Open No. 09-092613 discusses a technique, as another countermeasure, in which heat radiation is used to adjust temperature of a mask and a wafer.
An exposure apparatus has been known which moves a laser beam coming from a measuring device (ex. a laser interferometer) which measures the position of a stage, that holds a substrate and is moved, with the laser beam. The laser beam is moved so that it is always incident on a light reflection surface of the upper surface of the stage. It is difficult, however, to arrange a radiation plate in the exposure apparatus because the optical path of the laser beam needs to be ensured. Even if the radiation plate can be arranged, if a necessary cooling capacity cannot be ensured, countermeasures for that are required.